1. Field of the Invention
The present invention relates to a wiring structure for a head suspension, the head suspension supporting a magnetic head to write and read data to and from a magnetic disk (hard disk) in a magnetic disk drive of, for example, an information processing unit such as a personal computer.
2. Description of Related Art
The magnetic disk drives or hard disk drives are required to realize a high recording density. For this, a floating amount of the magnetic head of the head suspension from a recording face of a hard disk on which the head suspension operates must be minimized. In recent years, the floating amount is in the order of ten nanometers.
Reducing the floating amount of the head, however, results in increasing a risk of the head hitting very small projections if exist on the surface of the hard disk. In addition, the head involves an individual clearance variation in a tolerance range, and therefore, the floating amount of the head is unable to be lowered below the tolerance range, or the head will hit the hard disk.
To deal with this problem, Japanese Unexamined Patent Application Publication No. 2008-52882 proposes a technique of incorporating a heater in the head of the head suspension. The heater is energized to thermally expand, thereby controlling a clearance between the head and a recording face of the hard disk.
This related art employs a low-heat-expansion layer having a piezoelectric sensor structure. If a medium-confronting surface of the head protruding toward the hard disk due to energization of the heater coil hits a medium surface of the hard disk, a shock is applied to the piezoelectric sensor structure, which outputs a shock-corresponding voltage from a signal output terminal to the outside.
The shock-corresponding voltage is used to control a current to the heater coil, thereby controlling the floating amount of the head from the recording face of the hard disk.
As another related art, Japanese Unexamined Patent Application Publication No. 2008-152868 discloses a heat assist magnetic head having a near-field light emitter (plasmon probe) to emit near-field light to heat the recording layer of the magnetic disk, thereby thermally stabilizing magnetization of the recording layer.
The head suspension arranged in the hard disk drive has a flexure. The flexure has a four-layer structure including a base material made of a resilient stainless thin plate, a base insulating layer of flexible resin formed on the base material, wiring formed on the base insulating layer and connected to the head of the head suspension to transmit write/read signals, and a cover insulating layer of flexible resin formed over the wiring.
To such a wiring structure of the flexure, simply adding wiring for the above-mentioned heater, sensor, heat assist element, and other devices will cause a problem of widening the flexure.
The wiring for the additional devices such as the heater, sensor, and heat assist element must minimize a power loss to reduce power consumption. A signal frequency used by the sensor is less than or equal to 1/10 of that of a write signal, and therefore, the sensor needs narrow-band wiring because wide-band wiring is unable to suppress noise. The wiring for the additional devices, therefore, must be wide. This requirement, however, results in widening the flexure and making it difficult to miniaturize the head suspension.